This invention relates to an impact printing mechanism, and more particularly to an impact printing mechanism wherein a plurality of type plates are employed which each carry thereon a number of types arranged in rows and columns.
Typewriters are already known in which a great number, for example, thousands, of character types are incorporated. Typically, a conventional Japanese typewriter including kanas, kanjis, alphabets, numerals, symbols and so on. Such types are formed into individual type pieces or blocks and accommodated in rows and columns in a type box mounted for movement within a type accommodating plane to bring a selected type block to a particular position so that the type block may then be picked up and struck by a single type bar against a platen. Such type blocks are normally made of a type metal, resulting in significant weight of the machine. Besides, the machine must always be held in a horizontal position, since otherwise some or all of the types in the machine will drop from the type box.
A printing mechanism which eliminates these defects has been already proposed in a Japanese patent publication No. 51-26083. This prior art mechanism includes a set of type plates which each have a plurality of character types arranged in rows and columns thereon and are disposed in parallel relationship to one another and to a platen. A desired type is thus selected by three dimensional motions including a first motion of the type plate set in a first horizontal direction perpendicular to the planes of the type plates below the platen to bring a particular type plate containing the desired character type to a predetermined plane (i.e., selection of a type plate), a second horizontal motion of the type plate set in a second horizontal direction parallel to the platen to bring a type column including the desired type to a particular lateral position opposing a print hammer (i.e., selection of a type column), and a third vertical motion of the type plate within the predetermined plane to bring a type row containing the desired type to a position level with the print hammer (i.e., selection of a type row) thereby to finally position the desired character type in position in alignment or register with the print hammer to allow the type to be thereafter struck by the print hammer for effecting printing of the character. However, while a concept of such an arrangement is disclosed in the patent publication, it totally fails to disclose a practical structure for mounting type plates and a mechanism for selecting a character type from a number of characters on a set of type plates.